by Ishita Walia, Julian Lemmerer and Miranda Zhang
This part of the project was all about reaching the technical limits. The AudioMoth modules we used were equipped with a 128GB MicroSD Card and had 6000 mAh of battery life.
We opted to swap out SD cards and recharge the modules every month (31 days), so it was about managing the available storage and battery capacity, to last us one whole month. We soon figured out that battery life was not a problem at all, with the 6000 mAh being far more than we needed. So our main limiter was the 128GB SD card: The first thing affecting the storage when recording were the sampling rates. We chose a sampling rate of 96 kHz, which was actually far below the possible maximum sample rate of 384 kHz, but still it was just right for our application.
Now it was time to think about when to record our audiodata. Since we wanted to avoid some of the artificial sounds like traffic, while including natural sounds like bird singing, we agreed on recording the dawn-hours, which we estimated to be around 4:30-6:30. During this time we can hear the beautiful sounds of the so-called “dawn chorus” which the project is named after. Since we still had storage left, we also included the dusk-hours, 20:00-22:00, where we estimated to hear ultrasonic sounds from bats and added another hour of recording time right at the peak of the sun at 13:00. This resulted in our current recording times:
- Sunrise (& Dawn): 4:30 - 6:30 → morning dawn chorus
- Midday (Peak of the sun) 13:00-14:00
- Sunset (& Dusk): 20:00 - 22:00 → Night active animals (bats)
AudioMoth.config
{
"timePeriods": [{"startMins":150,"endMins":270},{"startMins":630,"endMins":720},{"startMins":1080,"endMins":1200}],
"ledEnabled": true,
"lowVoltageCutoffEnabled": true,
"batteryLevelCheckEnabled": true,
"sampleRate": 96000,
"gain": 2,
"recordDuration": 595,
"sleepDuration": 5,
"customTimeZoneOffset": 120,
"localTime": false,
"firstRecordingDateEnabled": false,
"lastRecordingDateEnabled": false,
"dutyEnabled": true,
"passFiltersEnabled": false,
"filterType": "none",
"lowerFilter": 0,
"higherFilter": 0,
"amplitudeThresholdingEnabled": false,
"amplitudeThreshold": 0.001,
"minimumAmplitudeThresholdDuration": 0,
"frequencyTriggerEnabled": false,
"frequencyTriggerWindowLength": 64,
"frequencyTriggerCentreFrequency": 24000,
"minimumFrequencyTriggerDuration": 0,
"frequencyTriggerThreshold": 0.001,
"requireAcousticConfig": false,
"dailyFolders": false,
"displayVoltageRange": false,
"amplitudeThresholdScale": "percentage",
"version": "1.10.2",
"energySaverModeEnabled": false,
"disable48DCFilter": false,
"lowGainRangeEnabled": false,
"timeSettingFromGPSEnabled": false,
"magneticSwitchEnabled": false
}
AudioMoth.config (bats expected)
{
"timePeriods": [{"startMins":150,"endMins":270},{"startMins":1080,"endMins":1200}],
"ledEnabled": true,
"lowVoltageCutoffEnabled": true,
"batteryLevelCheckEnabled": true,
"sampleRate": 384000,
"gain": 2,
"recordDuration": 595,
"sleepDuration": 5,
"customTimeZoneOffset": 120,
"localTime": false,
"firstRecordingDateEnabled": false,
"lastRecordingDateEnabled": false,
"dutyEnabled": true,
"passFiltersEnabled": false,
"filterType": "none",
"lowerFilter": 0,
"higherFilter": 0,
"amplitudeThresholdingEnabled": false,
"amplitudeThreshold": 0.001,
"minimumAmplitudeThresholdDuration": 0,
"frequencyTriggerEnabled": false,
"frequencyTriggerWindowLength": 64,
"frequencyTriggerCentreFrequency": 96000,
"minimumFrequencyTriggerDuration": 0,
"frequencyTriggerThreshold": 0.001,
"requireAcousticConfig": false,
"dailyFolders": false,
"displayVoltageRange": false,
"amplitudeThresholdScale": "percentage",
"version": "1.10.2",
"energySaverModeEnabled": false,
"disable48DCFilter": false,
"lowGainRangeEnabled": false,
"timeSettingFromGPSEnabled": false,
"magneticSwitchEnabled": false
}